[linux-lvm] Very slow i/o after snapshotting

Marian Csontos mcsontos at redhat.com
Tue Jul 9 12:19:16 UTC 2013

On 07/09/2013 01:51 PM, Micky wrote:
>> Is this supposed to be a bug report ?
> Sorry for bashing the info. I was just answering the questions. LOL!
>> So far I've no idea about disks/tables in use, system/kernel in use, lvm
>> version in use....
> RHEL 6.4 kernel-2.6.32-358.el6 (also tested with self compiled 3.8)
> lvm2-2.02.98-9.el6.x86_64
> Disk on external mega raid controller with ext4

How does it perform without snapshot? I have seen a sluggish RAID array 
when run out of battery.

Is there a reason to use that big chunks?
If the origin is seeing a lot of small dispersed writes using big chunk 
may multiply it manyfold (actually worst case 128-times: every 4k write 
generating 512k read from origin and then written to snapshot.)

-- Marian

> Running Xen hypervisor but tested without it as well
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